Re: [Xen-users] Just some (probably useless) information

[Brandon Lamb <brandonlamb@xxxxxxxxx>]

On Sun, Mar 21, 2010 at 8:43 AM, Pasi KÃrkkÃinen <pasik@xxxxxx> wrote:
> On Sat, Mar 20, 2010 at 12:37:34AM -0700, Brandon Lamb wrote:
>> I did a very non scientific test for speeds of backing up disk/file
>> images to disk/file backups
>>
>> I used lvm for both the disk based and to put the files onto during
>> the test. I used four 640gig sata 3.0gbps drives in a raid 10. There
>> was 2083 megabytes used on the filesystem, a windows xp install.
>>
>> dd disk -> disk = 36 minutes
>>
>
> Did you specify bigger block size for dd?:
> dd bs=1024k
>
> That should speed up things a lot.
>
>> ntfsclone disk -> disk = 4 minutes
>>
>> ntfsclone disk -> file = 2 minutes
>>
>> cp file -> file = 11 seconds
>>
>> So now I am left with the question of do I use file based images which
>> will have slower performance but super fast backup times, or go with a
>> lvm -> disk/file for the backup.
>>
>> My particular use case will be a user gets a 20 gig drive for xp,
>> their it guy will do manual image backup creation. If they blow up
>> their windows box we will have a "click click" ok now they are running
>> againback up using the backup disk/file image. If I use all disk based
>> images then I will have to also create a file backup of the backup
>> disk for my remote backup box to save in case the host dies.
>>
>
> Did you try lvm snapshots?
>
> XCP also supports vhd snapshots.
>
> -- Pasi

I think there may have been some confusion. The lvm partition was 20
gigabytes, the USED space was 2 gigabytes. So for dd it had to copy
all 20 gigabytes to another 20 gigabyte disk/file whereas using the
ntfsclone only copied the USED 2 gigabytes.

I dont think snapshots would really help in this case because when a
backup of the disk is made, it may not be backed up again for a week,
or a month, or a year which I dont think works with the snapshot
model? I am also not doing a live snapshot/copy, the guest vm will be
shutdown then the disk or file copied to another disk/file.

I'll try the blocksize tip and see what that gets me.

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